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Today's Topics:
1. Re: HUnit - testing for failed pattern match (Xavier Shay)
2. Re: HUnit - testing for failed pattern match (Daniel Fischer)
3. Re: HUnit - testing for failed pattern match (Xavier Shay)
----------------------------------------------------------------------
Message: 1
Date: Sat, 26 Feb 2011 12:08:48 +1100
From: Xavier Shay <[email protected]>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 24/02/11 12:31 AM, Edward Z. Yang wrote:
> Excerpts from Xavier Shay's message of Tue Feb 22 20:25:28 -0500 2011:
>>
>> On 23/02/11 10:35 AM, Edward Z. Yang wrote:
>>> What you describe is one of the cases when a partial function is ok
>>> (though it's probably better to do something like:
>>>
>>> giveMeThree x
>>> | x == 3 = True
>>> | otherwise = error "giveMeThree: not three"
>>>
>>> It's frequently not possible, but if you can arrange your types so that
>>> the invalid values are not possible, even better.)
>> ah that's good, I can give a helpful error message.
>>
>> Still would like a way to test it though...
>>
>
> Check the section "Testing for expected errors" herE:
>
> http://leiffrenzel.de/papers/getting-started-with-hunit.html
Excellent. I had to update the code to use the new Control.Exception
(rather than Control.OldException), and ended up with:
import Control.Exception
TestCase $ do
handle (\(_ :: ErrorCall) -> return ()) $ do
evaluate ( myFunc 3 [False, False, True] )
assertFailure "must raise an error on invalid state"
The only issue is that I now require the -XScopedTypeVariables flag,
otherwise it fails to compile with:
Illegal signature in pattern: ErrorCall
Use -XScopedTypeVariables to permit it
I am not sure whether this is an acceptable solution or not. I tried
reading this:
http://www.haskell.org/ghc/docs/latest/html/users_guide/other-type-extensions.html#pattern-type-sigs
... but I don't know enough about haskell for it to make any sense to me
yet.
Cheers,
Xavier
------------------------------
Message: 2
Date: Sat, 26 Feb 2011 02:36:41 +0100
From: Daniel Fischer <[email protected]>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
On Saturday 26 February 2011 02:08:48, Xavier Shay wrote:
>
> Excellent. I had to update the code to use the new Control.Exception
> (rather than Control.OldException), and ended up with:
>
> import Control.Exception
>
> TestCase $ do
> handle (\(_ :: ErrorCall) -> return ()) $ do
> evaluate ( myFunc 3 [False, False, True] )
> assertFailure "must raise an error on invalid state"
>
> The only issue is that I now require the -XScopedTypeVariables flag,
> otherwise it fails to compile with:
>
> Illegal signature in pattern: ErrorCall
> Use -XScopedTypeVariables to permit it
>
> I am not sure whether this is an acceptable solution or not.
ScopedTypeVariables is harmless, so it is accetable. But if you prefer, you
can avoid it with a top-level handler
ignoreErrorCalls :: ErrorCall -> IO ()
ignoreErrorCalls _ = return ()
TestCase $
ignoreErrorCalls $ do
evaluate ( myFunc 3 [False, False, True] )
assertFailure "must raise an error on invalid state"
or an explicit pattern in the handler,
TestCase $
handle (\(ErrorCall _) -> return ()) $ do
evaluate ...
I think (code untested).
> I tried reading this:
> http://www.haskell.org/ghc/docs/latest/html/users_guide/other-type-exten
>sions.html#pattern-type-sigs
>
> ... but I don't know enough about haskell for it to make any sense to me
> yet.
>
> Cheers,
> Xavier
------------------------------
Message: 3
Date: Sat, 26 Feb 2011 12:47:38 +1100
From: Xavier Shay <[email protected]>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 26/02/11 12:36 PM, Daniel Fischer wrote:
> On Saturday 26 February 2011 02:08:48, Xavier Shay wrote:
>>
>> Excellent. I had to update the code to use the new Control.Exception
>> (rather than Control.OldException), and ended up with:
>>
>> import Control.Exception
>>
>> TestCase $ do
>> handle (\(_ :: ErrorCall) -> return ()) $ do
>> evaluate ( myFunc 3 [False, False, True] )
>> assertFailure "must raise an error on invalid state"
>>
>> The only issue is that I now require the -XScopedTypeVariables flag,
>> otherwise it fails to compile with:
>>
>> Illegal signature in pattern: ErrorCall
>> Use -XScopedTypeVariables to permit it
>>
>> I am not sure whether this is an acceptable solution or not.
>
> ScopedTypeVariables is harmless, so it is accetable. But if you prefer, you
> can avoid it with a top-level handler
>
> ignoreErrorCalls :: ErrorCall -> IO ()
> ignoreErrorCalls _ = return ()
>
> TestCase $
> ignoreErrorCalls $ do
> evaluate ( myFunc 3 [False, False, True] )
> assertFailure "must raise an error on invalid state"
>
> or an explicit pattern in the handler,
>
> TestCase $
> handle (\(ErrorCall _) -> return ()) $ do
> evaluate ...
>
> I think (code untested).
tested the latter - totally works
case closed!
Thanks,
Xavier
------------------------------
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